In 1984, the researchers in Institute of Hydrobiology, Chinese Academy of Sciences firstly developed the study concerning directive breeding in fishes by gene engineering in the world, and established an intact theory model for transgenic fishes and a perfect technique system for experiment (Zhu, Z., Li, G., He, L. and Chen, S. (1985)). Novel gene transfer into the fertilized eggs of goldfish (Carassius auratus L. 1758). Journal of Applied Ichthyology 1: 31–34. 2, Zhu, Z., Xu, K., Xie, Y, Li, G. and He, L. (1989). A model of transgenic fish. Scientia Sinica B (2): 147–155). On this basis, the study concerning the rapid growth of carp transformed with the “all-fish” growth hormone gene acquired important development. The test of large-scale breeding showed that the average weight of the offspring population of transgenic carp was 42% higher than that of the offspring population of the control fish, and that the available efficiency of bait increased 18.5% and that moreover comprehensively economic benefit of pond culture increased 125.7%. Meanwhile, the study concerning rapid growth of transgenic rainbow trout, Atlantic salmon and java tilapia and like in Europe and America also acquired important development, and the large-scale breeding tests thereof were also performed. However, hitherto, the commercial example of transgenic fishes has not been reported.
Indeed, as a directive-improved organism by genetic methods, the biological safety of transgenic fishes is concerned generally throughout the society. The biological safety of transgenic fishes comprises consumable safety of transgenic fish as food and genetic safety for releasing and ecological safety. Now, the study concerning transgenic fishes utilizes the gene component originated from fishes even themselves which eliminates the hidden danger of safety of transgenic fishes as food. Moreover, the test results for detecting the food safety of carps transformed with “all-fish” gene also showed that it is not remarkable influence for the growth, development and reproduction of the mouse after taking transgenic fishes (Zhang, F., Wang, Y., Hu, W., Cui, Z., Zhu, Z., Yang, J. and Peng, R. (2000) Physiological and pathological analysis of the mice fed with “all-fish” gene transferred Yellow River carp. High Technology Letters 10: 17–19). The establishment of high efficiency breeding model and the study results of food safety provide a basis for allowing the transgenic fishes commercial. Therefore, there is a need to solve the hereditary and ecological safety problems as well as the controlling technique thereof in the study of transgenic fishes, which is also a prerequisite for achieving the industrialization of transgenic fishes. The hereditary and ecological safety problems of transgenic fishes comprise two aspects generally: first, the Genebank contamination of natural species resources resulting from the possible crossing between transgenic fishes and wild species and close relative species; and second, the population structure of the ecosystem in the water would be destroyed which results in an irreversible influence if transgenic fishes form dominant population. However, on the one hand, the genetic shift of transformed genes by sexual mating can be controlled by preparing the sterile transgenic fishes, and on the other hand, the formation of dominant population of transgenic fishes escaping into the natural water system which further results in unadvantageous influence for the ecosystem in the water can be prevented by preparing the sterile transgenic fishes. Thereby, the hereditary and ecological safety of transgenic fishes can be solved by controlling the reproduction of transgenic fishes.
Now, the breeding for sterile transgenic fish utilizes triploid strategy, that is to say, crossing diploid transgenic fish with tetraploid fish to obtain sterile triploid transgenic fish (Zhu Z and Zeng Z, open a door for transgenic fish to market, Biotechnology Information, 2000, 1: 1–6). However, it is very difficult to obtain tetraploid. The allotetraploid crucian-carp obtained by Chinese researchers without chemical or physical treatment is only tetraploid fish with stable hereditary characters in the world that can reproduce by itself (Liu S, Liu Y, Zhou G et al, The formation of tetraploid stocks of red crucian carp×common carp hybrids as an effect of interspecific hybridization. Aquaculture, 2001, 192(2–4): 171–186). Therefore, the use triploid strategy for breeding sterile transgenic fishes is restricted to a great extent, and said strategy is only a specific example for solving the hereditary and ecological safety of transgenic fish and thereby does not possess generality.